A four-sector cross-shaped urban microcellular system with intelligent switched-beam antennas is proposed. Each sector covers a street block with a base station located at an intersection, and an intelligent beam-switching scheme is used to locate mobile users in the most suitable beam coverage. Due to directional narrow-beam patterns and waveguide effects of tall buildings, radio signals along...

Experiment and simulation demonstrate high power microwave generation at 9 GHz using a 9-cm-diam, 44%keV, 7-kA annular electron beam. The beam is propagated in a coaxial drift tube between inner and outer conductors, a configuration which increases the available beam current and reduces the surface fields from existing high power sources. The microwave interaction is provided by an extended len...

the modulation response, relative intensity noise and frequency noise characteristics of qd lasers are investigated theoretically, in presence of an additional optical pumping. it is revealed that the modulation response of qd laser enhances under additional optical beam. by small signal analysis of the carriers' and photons' rates, it is proposed that by injecting excess carriers to ...

An incoherent combination of laser radiation from multiple sources into a single near-diffraction-limited beam is an important problem of high power laser design. Energy brightness, but not spectral brightness, can be increased using spectral beam combining (SBC). Initially, SBC was proposed on the basis of conventional surface gratings [1]; however, it was found later that volume Bragg grating...

v-shaped and triangular cantilevers are widely employed in atomic force microscope (afm) imaging techniques due to their stability. for the design of vibration control systems of afm cantilevers which utilize patched piezo actuators, obtaining an accurate system model is indispensable prior to acquiring the information related to natural modes. a general differential quadrature element method (...

A novel optical-trap method for improving the trapping capability using a radially polarized narrow-width annular beam (NWAB) has been proposed. In this paper, we theoretically study the tight focusing properties of a radially polarized NWAB, formed by subtly blocking the central portion of a radially polarized Bessel–Gaussian beam (the original doughnut beam), through a high-numerical aperture...

Thin film ablation with pulsed nanosecond lasers can benefit from the use of beam shaping optics to transform the Gaussian beam profile with a circular footprint into a Top-Hat beam profile with a rectangular footprint. In general, the quality of the transformed beam profile depends strongly on the beam alignment of the entire laser system. In particular, the adjustment of the beam shaping elem...

A digital fast feedback system for beam energy and position stabilization at the target of the CEBAF accelerator is capable of suppressing beam motion in the frequency band from 0 to 80 Hz and also performs narrow band suppression at the first twelve power line harmonics. The system utilizes two VME computers and runs at a 2.4 kHz sampling rate. The numerical algorithm is based on a recursive d...

In this paper, a displacement-based, variationally consistent, two variable refined theory for shear deformable beams is presented. The beam is assumed to be of linearly elastic, homogeneous, isotropic material and has a uniform rectangular cross-section. In this theory, the beam axial displacement and beam transverse displacement consist of bending components and shearing components. The assum...

Optical transition radiation (OTR) imaging for transverse beam-size characterization is a well-established technique at many accelerators including the Fermilab A0 photoinjector (A0PI) facility. With low beam energies of 14-15 MeV and emittances of 3 mm mrad, one observes beam sizes of 0.8 to 1.5 mm (sigma). However, the use of 50-μm wide slits to sample the beam’s transverse phase spaces signi...